The four stroke, at least the one I had, the throttle was on the other side of the carb (left side if viewing from the rear). That made for some interesting linkage setup in the plane that I had that engine installed. I had to carve some of the fuselage cheek next to where the carb linkage was to make clearance.

So, if you decide to go four stroke, make sure you look such things over.

One more thing I might suggest, no matter what method you finally decide on: avoid is metal-to-metal contact at the carb throttle arm. Some are made of plastic, so if that's the case, then it won't be a problem. But some are made of metal. So, avoid using a metal clevis to make the connection. I use these neat little plastic Dubro Ball Socket gizmo's that work great. The ball attaches to the throttle arm and the socket attaches to the hardware you use for the linkage from the servo, for a 40 - 60 size, you might use 2-56 hardware.

I use a length of Sullivan Golden Rod with a 2-56 threaded rod that has been screwed into the center of the golden rod. The golden rod is flexible and strong. Just provide two or three hard points for the guide tube along the path from the servo through the firewall. Scrape or sand the surface of the guide tube a bit, enough for epoxy to 'grab' on to at the hard points. The golden rod will slide easily through the guide tube so you can 'steer' it around any obsticals (within reason). Then attach the ball socket to the 2-56 rod, and adjust the opposite end (servo) for the correct length and put a clevis on there and off you go.